Broadband signals are, for example, request signals or data signals which are transmitted from a subscriber to a center in the upstream frequency band of a distribution network with a return (upstream) channel. EP 0 422 032 B1 discloses a data transmission apparatus for a cable television distribution network with a return channel by means of which data of a subscriber is transmitted to a center (head end) in the upstream frequency band using spread-spectrum techniques. Stationary interference signals caused by broadcasts may enter a cable television distribution network and may adversely affect the transmission of the data in the upstream frequency band, since they lie in the same frequency band. The return channel uses the frequency band 5-30 MHz, for example. For error-free transmission of data at a high bit rate, e.g., 2 Mb/s, no sufficiently large interference-free frequency range is available in the return channel because of the great number of stationary interference signals. During despreading, however, the stationary interference signals are also multiplied by the spreading function and thus spread. As a result, portions of the interference signals appear in the frequency band of the broadband signals and cause a degradation in signal-to-noise performance.